Summary Overall, 36% of adult Americans, and 66% of Latinos, lack the level of health literacy needed to understand prescription drug information, such as the dosing instructions on medication container labels. Low health literacy and poor understanding of medication instructions are important contributors to health disparities. They lead to medication non-adherence, lack of chronic disease control, and excess health care utilization and costs. Interventions to enhance the content and format of prescription drug labels could improve medication management and reduce health disparities, particularly among patients with low health literacy or limited English proficiency. A recent Institute of Medicine report highlighted the importance of standardizing medication labels according to available evidence. However, few if any tools have been developed to create and print evidence-based labels, or to accurately translate simplified dosing instructions into other languages. This proposal seeks to develop and evaluate PlainLanguageRx, an innovative technology platform that will enable pharmacists to rapidly produce evidence-based medication container labels in English or Spanish. The Specific Aims are to: 1) Finalize the design of a clearly-formatted, evidence-based medication container label, known as PlainLanguageRx;2) Develop the PlainLanguageRx software platform that will allow pharmacists to rapidly create evidence-based medication container labels;and 3) Conduct a randomized controlled trial to evaluate the effect of PlainLanguageRx labels, compared to traditional medication labels, on patients'understanding of their medication dosing instructions. The project team consists of experienced software engineers and academic physicians with expertise in business development and clinical research among underserved populations. For Aim 1, we will conduct focus groups and interviews with English- and Spanish-speaking patients, pharmacists, and leading national experts who have agreed to serve as key informants and guide the final label design. In Aim 2, we will develop the PlainLanguageRx software platform and conduct user testing with pharmacists and pharmacy staff to optimize its usability, efficiency, and acceptability. For Aim 3, we will conduct a randomized trial of 400 patients who fill prescriptions at an academically-affiliated community pharmacy. Patients in the intervention group will receive their medications with PlainLanguageRx labels, while those in the control group will receive usual care. The study will evaluate the effect of the PlainLanguageRx labels on patients'understanding of their medication regimen (primary outcome), as well as their self-reported adherence and satisfaction (secondary outcomes). Through a process of development and evaluation that is focused on the needs of both patients and pharmacists, our goal is to produce a software platform that facilitates the rapid creation of evidence-based labels and improves patients'understanding of their medication instructions. This will set the stage for subsequent efforts to disseminate this technology as a strategy to reduce health disparities. PUBLIC HEALTH RELEVANCE: Relevance According to an Institute of Medicine report, prescription drug information in the United States is overly complex and is misunderstood by many Americans, particularly those with low health literacy or limited English proficiency. This proposal seeks to develop and evaluate PlainLanguageRx, an innovative and affordable technology that will enable pharmacists and pharmacy staff to rapidly create clearly-formatted, evidence-based prescription drug labels in English or Spanish. By helping patients better understand and adhere to medication instructions, this technology has potential to improve disease control and reduce health disparities among groups with low health literacy or limited English proficiency.